This invention is concerned with the welding of cast iron and the joining of cast iron to itself or to other materials, such as any type of ferrous metal, copper, or bronze.
In the past, the welding of gray cast iron has posed substantial problems. The two types of welding electrodes which are commonly used for the welding, joining and repair of cast iron are (1) a 99% nickel rod coated with conventional flux coatings (typically comprising alkaline earth metal carbonate and fluorides and silicate binders) and (2) a 55% nickel, 45% iron alloy coated with a similar flux. The fluxes may contain small amounts of carbon, manganese, and a trace of silicon. These welding electrodes generally are utilized with direct current, reverse polarity welding machines, and they preform quite poorly with alternating current machines.
The more generally used of these two electrodes is the 55% nickel, 35% iron alloy. This alloy has extremely poor electrical conductivity properties, in fact various types of nickel-iron alloys, commonly referred to as calrods, are used for electric stove heating elements and the like. The high electrical resistence of the 55% nickel, 45% iron alloy makes its use in welding difficult and often impractical. For example, a 14-inch electrode which is 1/8 inch in diameter will reach a temperature of approximately 1200.degree. F when consumed about 50% at 115 amps, and when 65% consumed, the electrode will be red hot at a temperature of approximately 1500.degree. F. In order to consume the complete electrode in a welding operation, extra care and heat adjustments, along with a low degree of control is used, making the welding quite difficult and time consuming. The use of the 99% nickel electrode with conventional flux coatings results in a weld having quite poor physical characteristics.
As a result of these problems, the present techniques for welding cast iron leave much to be desired.
In the prior art, U.S. Pat. No. 3,301,997 proposes welding ductile iron using a nickel-iron alloy rod capable of depositing a nickel-iron alloy. Here the welding rod itself is an alloy and suffers from the problems of over-heating, limited utility, etc above explained.
U.S. Pat. No. 2,471,803 discloses a flux for application to steel, nickel, monel metal, bronze and the like rods. The flux contains iron only in the form of ferro-chrome, ferro-silicon, or deoxidizing alloys in limited amounts only (up to 5% each). Obviously, it is impossible to introduce substantial amounts of iron into the weld metal alloy, when using a nickel core rod.
Canadian Pat. No. 625,690 proposes a welding electrode having a core material of steel, nickel-iron alloy or nickel coated with a flux containing a silicon, nickel and/or iron in the form of a fine powder to make the flux conductive. There is no definition of the weld metal composition and there is no suggestion of forming an iron-nickel alloy during welding.